On Tue, 23 Apr 2013 19:05:53 +0200, Attila Kinali <[email protected]> wrote:
>On Tue, 23 Apr 2013 09:49:19 +0400 >Daniel Ginsburg <[email protected]> wrote: > >> Not perfect, but should be reasonably good. It's an external magnetic >> antenna on my windowsill. >> Anyway, +-400ns I'm seeing translates to +-120m in position. My surveyed >> location is better than this. > >Windowsill? So you have only partial view of the sky? >Then those 400ns sound about right. Said Jackson reported a couple >of months back that a LEA-6T showed about 1us (IIRC) jitter until >he avaraged the position for a couple of days (weeks?) to get the >real position. After that, the jitter was much better. >He also send some nice graphs of those measurements. You might want >to look for them in the archives. > > Attila Kinali I always suspected something like this was at work. This would explain the ambiguous 1uS specification common in GPS receivers that are not intended for rigorous timing applications which I asked about a couple months ago. I did not ask the right question. :) With this in mind, I would assume that averaging over multiples of 12 hours would be necessary for maximum accuracy and days would be required to account for atmospheric transmission effects. Now I have a much better idea about how good the disciplined oscillator will need to be. A receiver intended for timing applications using position hold should allow accurate locking in a hundredth the time or less. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
